Pressure-sensitive adhesive tape which is wound upon itself in roll form generally has a low-adhesion backsize coating to permit the tape to be unwound without delaminating. The force required to separate such a tape from the low-adhesion backsize coating typically ranges from 150 to 900 grams per 2.5 cm of width. If the tape is not wound upon itself or is an adhesive transfer tape in roll form, its adhesive coating is customarily protected by a disposable web which likewise has a low-adhesion coating to which normally tacky and pressure-sensitive adhesives adhere very weakly, e.g., a peel force of about 5 to 150 grams per 2.5 cm width and preferably 5 to 50 grams. This construction is useful for products such as adhesive coated labels or large adhesive coated sheets or in adhesive transfer tape construction. U.S. Pat. Nos. 3,230,289, 3,565,750 and 3,729,444 are illustrative of such products. Any such low-adhesion coating must both adhere strongly to its underlying substrate and be sufficiently cured or rendered incompatible with the adhesive so that it does not contaminate the adhesive, i.e., does not transfer into the adhesive and interfere unduly with its adhesiveness. Low-adhesion backsize coatings are disclosed, for example, in U.S. Pat. Nos. 3,318,852; 3,536,749; 4,057,596 and 4,216,252.
Certain pressure-sensitive adhesives, particularly those prepared from polydimethylsiloxane, are so aggressively tacky that tapes containing them require undesirably high peel forces to remove them from known low-adhesion coatings, especially after prolonged storage. The adhesives of such tapes may carry away and thus be contaminated by appreciable amounts of the low-adhesion material. Known low-adhesion coatings, e.g., polyurethane, polytetrafluoroethylene, and polydimethylsiloxanes, are especially ineffective for providing a peel force in the range of 5 to 50 grams per 2.5 cm width with polydimethylsiloxane adhesives.
Low-adhesion coatings have other uses, e.g., nonstick coatings for cooking utensils, ice-releasing coatings for aircraft, and lubricative coatings for magnetic recording media. Such low-adhesion coatings are sometimes called "release coatings", a term which also encompasses release agents for molds, which generally are effective only by failing cohesively. Lubricants that are uncured fluids or waxes usually function by cohesive failure. The release coatings of this invention are cured compositions which are designed to resist cohesive failure. To distinguish release coatings which are designed to fail cohesively from those which are designed to resist cohesive failure, the latter are herein called "liners" and, more specifically, "low surface energy liners" because low surface energy is important to their effectiveness.
Polyorganohydrosiloxanes useful for preparing the low surface energy coatings of the present invention are known in the art and are disclosed in U.S. Pat. Nos. 3,159,662; 3,220,972, and 3,410,886.
Ethylenically-unsaturated perfluoropolyether monomers useful in undergoing hydrosilation in the process of the present invention are disclosed in U.S. Pat. Nos. 3,810,874 and 4,321,404.